Study on Mass Transfer between Surface Water and Sub-Surface Water

本文对可渗透边界上的流动进行了实验研究，并利用流动显示技术揭示了：（1）可渗透边界可分为三层，位于边界顶部的A层是垂直质量输运最活跃的层;（2）可渗透边界的几何特征，即，长深比约为0.25，深度取决于边界的粒度;（3）表层和次表层沃茨之间物质输运的三个特征参数，即，通过量纲分析揭示了特征时间、质量交换速度、扩散系数与边界水力参数和特征参数之间的函数关系，并对地下水和河流沃茨的流动及质量输运进行了研究。（1）实验研究了盐的吸附曲线，明确了盐的吸附与解吸过程的滞后曲线。（2）利用饱和和非饱和渗流理论对水下与河流之间的流动进行了数值模拟，揭示了水流流速与河流水面高程的关系，并通过现场实测和室内实验研究了具有透水边界的水槽中浊度的浓度衰减规律。（1）用量纲分析法研究了其特征速度。（2）河流中浓度衰减的数值实验表明，河流中浓度衰减的原因是支流入流的稀释作用，以及河水与地下水流之间的物质输运和交换作用。

Flows on the permeable boundary was experimentally investigated, and the flow visualization technique revealed ; (1)permeable boundary is schematically classified into three layrs, and the layr A located on the top of boundary is the most active for vertical mass transport ; (2)its geometrical features, i.e., the length to depth ratio is about 0.25 and the depth is dependent on the grain size of boundary ; and (3)the three characteristic parameters of the mass transport between surface and sub-surface waters, i.e., the characteristic time, the mass exchange velocity, the diffusion coefficient were also investigated, and dimensional analysis disclosed the functional relationships between these three parameters, and hydraulic parameters and characteristic parameters of the boundary.Flows from the underground water and the river waters and associated mass transport was investigated. (1)The absorption curves of salt was experimentally investigated and the hysteresis curves between absorption and desorption processes were clarified. (2)The flows between the underwater and the river was numerically investigated by means of saturated and un-saturated seepage theory and it is disclosed that the flow rate depend on the water surface elevation of he river water.The concentration decay of the turbidity was also investigated by the field measurements and the laboratory study in the flumes with permeable boundaries. (1)Its characteristic velocity was studied by dimensional analysis.(2)The numerical experiment of the concentration decay in the river disclosed that it was caused by the dilution by the inflow from tributaries, and/or the mass transport and exchange between the river water and the sub-surface flows.